The Research On New DC Breaker For Metro System

With the rapid development of national economy and a huge population migration to the country's cities, the subway, as a pollution-free, faster and convenient urban traffic mode, is popular in many large or middle cities. The DC breaker used in the existing power supply system for subway is easily burned when there is extreme short circuit,which causes adverse impact to the maintain and operation of the subway. To solve the problem, based on the arc and simulation study on traditional DC breaker, this paper points out that it is the DC breaker's failure to burn out the DC arc with extreme short circuit caused the contact burning. The paper puts forward a new design concept of subway DC breaker and simulation is also carried out.The result indicates that the new DC breaker has meaningful results on preventing the arcing and fast-speed switching of DC breaker circuit.The whole simulation circuit is designed on the data from survey and study. After simplifying subway power supply system, the circuit introduce Mayr arc as the Main contact of the DC breaker, do research both on the traditional DC breaker and the new DC breaker based on the matlab platform. The paper gives out the selection of detail parameters of the Mayr model and circuit parameter. It also gives the principle of new DC breaker. The simulation of the traditional DC breaker shows that it is the failure to burn out the arc caused the contact burning, the simulation of the new DC breaker shows that it can reduce the arc and produce artificial zero value,change the DC arc extinguish to the AC extinguish. This makes it is more easy to put out the arc.The design of the new subway DC breaker includes the design of the breaker main circuit and design of the control device. Design Process of the main circuit gives the action and the Selection method of each part, the design of the control device includes two parts, they are hardware design and software design. Based on DSP2812, the control device has designed the parts of data acquisition board and data processing board and so on. The calculation of current and voltage value adopt FFT Function Library with the DSP. Make sure that it can calculate the data quickly and supply to the Control Segment to analyze.